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I5 750 -3.8ghz- its really not that easy...

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January 7, 2011 6:24:17 PM

Hello everyone. Im really sorry to have to post this thread, because from what ive been reading here and everywhere, overclocking an i5 750 is a piece of cake and easily done stably. Now I admit to being new to this but im reading as much as possible and ive already had some great advice regarding my RAM and getting the most out of that ( thanks Jaquith ). The thing is I now want to overclock my CPU and try and get it up to maybe 3.8, so im not being greedy ( i'll happily go further though if its stable). Ive built my sytem on a 850W corsair PSU, ive got swiftech watercooling, and ive got 16GB of corsair vengence RAM running at 1600mhz. It would be silly not to try and overclock i think. So ive read all the info i can find and start copying the suggested settings that have been posted over the internet and the highest i get to is 3374mhz. heres how. By the way ive got an asus p7p55d Mobo.

BCLK - 160
vcore-1.38v
loadline calibration- disabled
PCH-1.15V
PLL-1.9v
multiplier x21

ive set the RAM manually with the help of Jaquith to its potential

I know im missing something key but cannot find what, so can anyone please post an idiots list of settings for me to type into my bios to get it up to at least 3.8ghz, it would be very much appreciated.

More about : 750 8ghz easy

a c 100 K Overclocking
January 7, 2011 6:48:59 PM

PCH is the "southbridge" you don't really need to increase it, but it shouldn't hurt anything. I found it helped my GT 240 stabilize a bit, which is on my 4x lane to the southbridge as I already have both main 8x/8x lanes used for Crossfire...

But anyway...

With 21x multiplier, do you have EIST and C States on? If so, you're probably defaulting to a turbo boost OC which is more difficult to get stable.

Also you need to adjust VTT/IMC as well as Vcore for CPU stability. Your Vcore is very high for 160 base clock, so I have to assume your VTT is low. Of course it's always possible to get a dud CPU, which would suck.

You could just try 200 base clock, 19 multiplier. Turn LLC on. Probably around 1.3V Vcore, 1.2V VTT/IMC - somewhere in there. You can set your RAM to 1600mhz too.

IMO tho you really need to figure out the settings it needs for yourself. Things like EIST, C1E, C States, Spread Spectrum can all affect whether it gets stable or not.

There's nothing you can really do but try and learn.
January 7, 2011 8:43:41 PM

I think one of the places im going wrong is the Vtt/IMC because im not touching that anywhere. this is because i cant find where to adjust it in my BIOS. Basicaly one of the guides im following is the one posted under overclocking and benchmarking guides by randomizer. He uses a Gigabyte GA-P55A-UD5 M/B and as i couldnt find where it might be in my BIOS, I adjusted all the settings he suggested apart from the Vtt/IMC, stupidly assuming it was gigabyte Mobo specific. Any idea where those settings are in my BIOS or if ASUS call them something else.

thanks for the help so far by the way
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a c 100 K Overclocking
January 7, 2011 8:56:16 PM

Could be called QPI voltage as well
a c 131 K Overclocking
January 7, 2011 9:16:53 PM

I have never had too touch anything but BCLK up until about 177 with CPU multipliers of 21 or less
January 9, 2011 5:45:20 PM

Im still going. Ive been trying all sorts of different methods and combinations of BIOS settings. Ive finally managed to get it to run beyond 3214mhz by putting the BCLK to 210 and multiplier of 20, but to get it to boot ive had to drop the RAM to 1266MHZ i think it was. Its started up and now running 4213mhz CPU and so far stable under prime test. Its only been running an hour so far but fingers crossed.

If this works out ok can i assume a CPU@ 4.2ghz and 16gb of RAM at 1266mhz is better than a CPU@ 2.7ghz and 16gb RAM @ 1600mhz. I know that sounds stupid now ive written it but can anyone confirm that the faster CPU is a significantly better option.
a c 100 K Overclocking
January 10, 2011 2:04:49 PM

Yes, it is better usually but it kind of depends on your usage. Why not try 200x20 and 1600mhz RAM? Or you could even do 200x21 for the same CPU speed but with the RAM at it's proper speed.
January 10, 2011 5:49:32 PM

I couldnt get the last settings I posted past an hour with out a couple of errors, but ive had success with these i think

210 BCLK, 19 multiplier and RAM at 1260mhz which gave me 4ghz at the CPU. This ran on prime for 17 hours then threw up an error on 1 core and the rest carried on for 24 hours with any more errors at which point ive just stopped it.

I think im happy with that although i would like to get my RAM back to the 1600mhz that i started with. im going to write these settings down as i can always come back to them if i cant get any better.

I take it 17hrs until my first error is pretty stable or is that still not good enough?
a c 100 K Overclocking
January 10, 2011 6:22:06 PM

Yes that's pretty stable and should be fine. But like I posted in my last response, why not run 200 base clock at 20x, and then your RAM at 8x for 1600mhz? You should be able to use pretty much the same voltages.
January 10, 2011 6:45:45 PM

ive set the following now

BCLK 200, multiplier 19, RAM 1600mhz. ive left the multiplier at 19 for now to see how stable it is there first. This gives me 3.8ghz which is a little drop but not too bad. gonna leave that over night and see how it goes. Its and hour in now and no fails yet.
a c 100 K Overclocking
January 10, 2011 7:08:56 PM

Good stuff! I hope it works out.
January 10, 2011 9:31:01 PM

well that didnt work too well. I got fails on three cores after just an hour. I also gave these a quick go but the desk top froze on me as soon as windows started.

BCLK 210, multiplier 20 and RAM 1260 ( basically the same as the stable settings just with a multplier of 20 instead of 19)

It seems that pushing my RAM to its maximum 1600MHZ is where my fails are happening, so im at a loss now how to get the best out of it. Should i be happy running it at 1260mhz and having a stable OC of 4GHZ CPU or is there another option. I was wondering if I just need to up one of the voltages to keep the RAM happy. Any thoughts?

On the positive side, thanks to everyones help so far not only is my OC looking like its getting to where i want it , im learning something, so thanks for the pointers everybody.
January 11, 2011 12:51:03 AM

XMP? go into that profile... should set max mhz for your ram
a c 100 K Overclocking
January 11, 2011 1:42:58 AM

XMP will also set the baseclock to 160, which is lower than he wants.

Frankly, if your ram is rated for 1600mhz and you make sure all the timings are what they're rated for as well as the voltage, they should work. If they don't either they're defective or else the problem lies elsewhere.
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